A mower of this general type is known the drive means of which consists of wheels keyed on upwardly directed shafts and driven in rotation by a belt. This drive mechanism does not make it possible to assure a synchronous transmission of movement. The belt can slip on the wheels during working of the mower when one or the other of the cutting elements, which are connected to the wheels, is braked or locked for any reason, such as obstacles, piles of heavy hay, etc.
When desynchronization between two adjacent wheels reaches a certain value, and if the cutting elements are located at the same level, the cutting tools mounted on the cutting elements can collide. These collisions can cause breaking of the cutting tools or of their fastenings.
Considering the high rotating speed of the cutting elements, a cutting tool that is broken or torn from its cutting element can cause serious accidents to persons in the vicinity of the mower or even to the machine operator. Further, a cutting element that is equipped with a broken cutting tool or on which a cutting tool is missing performs unsatisfactory work.
To reduce this serious drawback, the known mower has two adjacent cutting elements offset vertically in relation to one another, so as to turn in different planes of rotation. Thus, the cutting tools of two adjacent cutting elements can no longer collide with one another even if the positions of the cutting elements are desynchronized.
The drawback of this known mower resides in the fact that the upwardly directed shafts of different adjacent cutting elements are different. This therefore requires the production of two or more kinds of shafts, which causes an increase in the cost of the machines.
Another mower of this type is known which also had adjacent cutting elements turning in different planes of rotation. On this mower, the upwardly directed shafts on which the cutting elements are mounted are identical, and the offset between the cutting elements is obtained with braces placed between the shaft and the cutting element which must be higher.
This other known mower has two drawbacks.
A first drawback resides in the fact that, during remounting of a high cutting element after a repair or a cutting element change, the repairer may fail to replace the braces between the shaft and cutting element. In this case, there is a serious risk of an accident as explained above.
A second drawback resides in the fact that it is necessary to produce additional parts, in this case, braces. This, therefore, also raises the cost of the machine.
Again, another mower is known which comprises a pair of adjacent cutting elements, one of which is inclined in relation to the other. This inclination enables the cutting elements to turn in different planes of rotation, while having front points of the end paths described by the cutting tools mounted on the cutting elements approximately at the same level in relation to the ground surface.
When this design is applied to mowers with cutting elements driven from below such as those now known (i.e., by simply inclining one of the cutting elements in relation to the adjacent cutting element), the cutting height becomes undesirably great. Considering the size of the cutting elements of these known mowers, the housing located under the cutting elements must have a sufficient thickness to allow the transmission means (such as a belt, for example) to go from the wheel of one cutting element to the wheel of the adjacent cutting element. This is undesirable.
Another great drawback of certain known mowers resides in the fact the front part of the housing slides on the ground and protects the cutting elements. The front part of the housing therefore is subjected to heavy wear and more or less great impacts which can wear out the housing. Moreover, since the housing is made in one piece, it is necessary to change it completely, which involves considerable expenses for the user.
On other mowers it is know to fasten on the front part of the housing additional parts by means of which the cutter bar slides over the ground and which protect the cutting elements. These parts can then be replaced when they are worn out. These additional parts, however, make the cutter bar heavy, which already requires a lightening device so that the cutter bar will rest lightly on the ground during operation. Moreover, these additional parts raise the cost of the mower.